1. Field of the Invention
The present invention relates generally to biocompatible electrodes and, more particularly, to a process of improving the sensing function of biocompatible electrode tips and products so made.
2. The Prior Art
Biocompatible electrodes are required in implants, such as for example, cardiac pacemakers. Among other considerations, implants need be as small as possible. Their electrode tips, however, must exhibit large surface areas. Such large surface areas at the tips of biocompatible electrodes are desirable, inter alia, so that the tips provide minimum contact resistance at any electrode-tissue interface. Consequently, electrode tips with large surface areas enhance the sensitivity of the pacemaker, are instrumental in keeping the voltage required for stimulation of the heart muscle low, and increase battery lifetime. The above in turn helps to reduce patient stress in allowing longer intervals between battery replacements.
In the beginning, biocompatible electrodes featured domeshaped tips with smooth exterior finishes. In the mid 1970's, workers in the field began experimenting with surface roughening techniques for biological implants, including the use of ion-beam sputtering. See A. J. Weigand et al., "Ion-beam-sputter modification of the surface morphology of biological implants," J. Vac. Sci. Technol., 14(1), Jan/ Feb. 1977, 326-331; H. R. Kaufman et al., "Ion beam texturing of surfaces," J. Vac. Sci. Technol., 16(2), Mar./Apr. 1979; A. J. Weigand, "Mechanical properties on ion-beam-textured surgical implant alloys," J. Vac. Sci. Technol., 15(2) Mar/Apr. 1978; Bruce A. Banks, "Ion Bombardment Modification of Surfaces in Biomedical Applications," Chapter 10, Ion Bombardment Modification of Surfaces, edited by O. Auciello and R. Kelly, published by Elsevier (1984); A. N. Curren et al of Lewis Research Center, "Process Produces Low-Secondary-Electron- Emission Surfaces, "NASA Tech Briefs, March/April 1986, pp. 89-90; A. J, Weigand, "The use of an ion-beam source to alter the surface morphology of biological implant materials," NASA TM-78851, Society for Biomaterials Conference, April/May 1978; and A. J. Weigand et al, "Mechanical and Chemical Effects of Ion-texturing Biomedical Polymers," NASA TM-79245, Thirty -second Annual Conference of Engineering in Medicine and Biology, October 1979. The thrust and emphasis of these early efforts have been directed, for the most part, at affecting the mechanical properties of surgical implant alloys, such as their ultimate strength and yield strength regarding hard tissue implants, such as dental implants, and connective tissue in-growth to assure mechanical attachment of and to the implant regarding soft tissue implants, such as vascular prostheses. As far as known, however, the electrical properties of biological implants in general, and of biocompatible electrodes in particular, have not as yet been addressed by or focused on by any worker in the field. There is thus room for improvements.